Spacex has launched the Falcon 9 rocket and the Dragon capsule

Musk has said the really "risky bit" is still to come, when the Dragon is due to descend after making two or three orbits at an altitude of 186 miles (300 kilometers). Splashdown could come as early as 2:02 p.m. ET. If the thrusters don't work just right, or if the craft's heat shield fails, the Dragon could literally go down in flames. But even then, the SpaceX team would be able to chalk up today's flight as a "75 percent success,"

If the entire mission goes as planned, it will mark the first time a private company has launched and re-entered a spacecraft from low-Earth orbit -- and could signal a new stage in NASA's plan to privatize the spaceflight industry.

SpaceX currently holds a $1.6 billion contract from NASA to transport cargo into space but not people.

SpaceX CEO Elon Musk, co-founder of PayPal, said in July that if all goes well after a series of test flights, SpaceX will be ready to begin flying cargo to the space station next year.

Musk says they can begin ferrying astronauts to the space station within three years.

The Dragon spacecraft is comprised of 3 main elements: the Nosecone, which protects the vessel and the docking adaptor during ascent; the Spacecraft, which houses the crew and/or pressurized cargo as well as the service section containing avionics, the RCS system, parachutes, and other support infrastructure; and the Trunk, which provides for the stowage of unpressurized cargo and will support Dragon’s solar arrays and thermal radiators.

In December 2008, NASA announced the selection of SpaceX’s Falcon 9 launch vehicle and Dragon spacecraft to resupply the International Space Station (ISS) when the Space Shuttle retires. The $1.6 billion contract represents a minimum of 12 flights, with an option to order additional missions for a cumulative total contract value of up to $3.1 billion.